" BLENDING" INHEKITANCE 



or two segregating factors, but involving sev- 

 eral such factors. Before entering into this ex- 

 planation it will be necessary to discuss a fur- 

 ther extension of Mendelian principles recently 

 made. 



Some modified Mendelian ratios of particular 

 interest have lately been obtained by the Swedish 

 plant-breeder, Nilsson-Ehle (1909, Lunds Uni- 

 versitets Arsskrift) in crossing varieties of 

 wheat of different color. When a variety hav- 

 ing brown chaff is crossed with one which has 

 white chaff, the hybrid plants are regularly 

 brown in F and 3 brown : 1 white in F 2 , but 

 a particular variety of brown-chaffed wheat 

 gave a different result. In 15 different crosses 

 it gave uniformly a close approximation to 

 the ratio 15 : 1 instead of 3 : 1. The totals are 

 sufficiently large to leave no doubt of this. 

 They are 1410 brown to 94 white, exactly 15 : 1. 

 This is clearly a dihybrid Mendelian ratio, and 

 Nilsson-Ehle interprets it to mean that there 

 exist in this case two independent factors, each 

 of which is able by itself to produce the brown 

 coloration, though no qualitative difference can 

 be detected between them. 



131 



